As known in the relevant technical field, an electronic device may comprise a microprocessor, a state machine, or digital components, and may need a scanning or timing signal for evolving from one state to another. Within this context, it may be important to accurately regulate the frequency of this timing or clock signal to maximize the performance of the system.
It is also known that dimensions and costs may be important aspects in the development of an electronic device. To the purpose of accurate regulation of the clock frequency, it may be suitable to use an oscillator of the integrated type, avoiding approaches comprising discrete components, such as, for example, quartz oscillators. However, although quartz oscillators may be characterized by good accuracy and a decrease in the final costs of the electronic device, they may have unacceptable dimensions for many applications.
Unfortunately, the characteristics and performance of an integrated oscillator may depend on the variations in the manufacturing technological process, the supply voltage variations, and the temperature variations. Thus, when designing such a device, a prerequisite may comprise checking the behavior of the device having the oscillator under all the possible operation conditions. Another prerequisite during design may be dimensioning and configuring each part of the device so that it operates correctly.
More particularly, it is the frequency of the integrated oscillator that undergoes great variations with respect to the desired value due to: the variations of the technological process, the variations in the supply voltage, and the variations in the temperature variation. At the end of the manufacturing process, it may be difficult to emphasize the importance of an accurate oscillator frequency, with respect to the optimum design frequency. Overcoming the limit value at which the digital circuits can switch correctly, may cause a failure of the system.
With respect to an optimum frequency set when designing the oscillator, which hereafter may be called target frequency fTARGET, it may be helpful to generate a frequency value lower than E·fx, where E is the highest percentage error due to: the manufacturing process variation, the supply voltage variation, and the temperature variation, and fx is the frequency at which the oscillator may effectively operate while being immune from the above variations. More precisely, the value of the percentage error may be due to three contributions, E=Ep+Ev+Et, respectively, due to the variations: of the manufacturing process, of the supply voltage, and of the temperature.
To compensate for these possible errors due to several processes, supply and temperature variations may be:fx+(fx·E)≦fTARGET  (1)
The highest value of fx is given by:fx+(fx·E)=fTARGET  (2)
Then:
                              f          x                =                              f            TARGET                                (                          1              +              E                        )                                              (        3        )            
From the relation (3), it may be appreciated that the lower the value of the percentage error E, then the closer the effective operation frequency value fx may move towards the fTARGET value, i.e. to the weighted value. At present, Applicants submit that it appears that no technical approach is known that allows automatic realization of dynamic tuning of the clock frequency in an oscillator so as to regulate its value at the end of the semiconductor manufacturing process.